Activation of hydrogenation catalysts



May 24, 1966 J. T. CABBAGE 3,253,048

ACTIVATION OF HYDROGENATION CATALYSTS Original Filed May 25. 1961 IMPUREH2 H PURE H2 12 1 X |6 HYDROCARBON IMPURITIES FUEL GAS *|5 REACTOR\/*FUEL GAS 27 I9 22 j 20 FUEL GAS 25 WATER INVENTOR.

J.T CABBAGE A TTOPNEVS United States Patent 1 Claim. (Cl. 260-667) Thisis a division of my application, Serial No. 112,- 591, filed May 25,1961, now Patent No. 3,186,956.

This invention relates broadly to the activation of metal hydrogenationcatalysts. In accordance with one aspect, this invention relates to animproved method of activating or reducing metal hydrogenationcatalyists, especially nickel-kieselguhr hydrogenation catalysts. Inaccordance with another aspect, this invention relates to the metalhydrogenation catalysts activated by the above process and to thehydrogenation of hydrocarbons, especially aromatic hydrocarbons, incontact with said catalyst.

In the hydrogenation of unsaturated compounds, and particularly in thehydrogenation of aromatic hydrocarbons, for example benzene, metalcatalysts are used. These metal catalysts are usually received from themanufacturer as metal oxide or other compound on a support such askieselguhr. The metal oxide or other compound must be reduced, at leastin part, to the metal before it is active for hydrogenation. Normally,this reduction step is accomplished with the catalyst in place in thehydrogenation reactor, but before the reactor is placed onstream forhydrogenation. This reduction step has been ordinarily carried out inthe prior art by employing pure hydrogen as the reducing medium.However, pure hydrogen is extremely expensive to use. Also, in someplant practices, steam is added to impure hydrogen as a diluent tocontrol the temperature rise during reduction of the catalyst. However,this has also been found to be undesirable since the catalyst life issomewhat less when employing steam as a diluent compared with a catalystreduced with commercial pure cylinder hydrogen.

According to the invention, 1 have found that various metalhydrogenation catalysts, particularly nickel hydrogenation catalysts,can be etiectively and efficiently activated or reduced prior to usewithout the prior art disadvantages by using an impure hydrogen streamas the reducing medium or atmosphere.

Accordingly, an object of this invention is to provide an improvedmethod for activating hydrogenation catalysts.

Another object of this invention is to provide an improved method foractivating or reducing nickel-kieselguhr hydrogenation catalysts.

A further object of this invention is to provide a novel reducing mediumor atmosphere for activating metal catalysts.

Another object of this invention is to provide an active metalhydrogenation catalyst especially a nickel hydrogenation catalyst, ofincreased catalyst life.

Other objects, aspects as Well as the several advantages of thisinvention will be apparent to one skilled in the art upon reading thisdisclosure and the appended claim.

Broadly, according to the invention, I provide an improved process foractivating or reducing metal hydro- 3,253,943 Patented May 24, I966genation catalysts, such as nickel-kieselguhr hydrogenation catalysts,which comprises contacting the catalyst at a temperature ranging fromabout 500 to 750 F. with a reducing atmosphere or medium comprising animpure hydrogen stream containing a minor proportion of at least onehydrocarbon material demethylizable at the temperature of contacting.Many of the prior art disadvantages are obviated when activating orreducing metal hydrogenation catalysts according to the invention.

According to one embodiment of the invention, an impure hydrogen streamcontaining a minor proportion of paraflinic hydrocarbons having from 2to about 6 carbon atoms obtained as an off-gas from a reformer operationis utilized as the reducing atmosphere or medium. In carrying out theinvention according to this embodiment, the reduction step can beconducted without the addition of steam which is normally used by theprior art methods.

In accordance with another embodiment of the invention, a residue gasobtained from the cracking of light hydrocarbons comprised principallyof hydrogen and containing a small amount of olefinic hydrocarbons isutilized as the reducing atmosphere. By operating according to thisembodiment, the activation or reducing step can be carried out on aonce-through basis without any added steam.

According to a further embodiment of the invention, I prepare an impurehydrogen stream for reducing metal hydrogenation catalysts prior to useby adding a controlled amount of at least one demethylizable hydrocarbonmaterial to a pure hydrogen stream (cylinder hydrogen) and then passthis mixture over the catalyst bed to activate same. By carrying out theinvention according to this embodiment, the addition of steam diluent isnot required and the reducing gas can be passed over the catalyst on aonce-through basis. In addition, if equipment is available, recycle canbe efiected.

The impure hydrogen streams that I prefer to utilize as the reducingmedium for activating metal hydrogenation catalysts according to theinvention are ordinarily obtained as a hydrogen-rich residue gas streamrecovered from a hydrocarbon conversion process. Ordinarily, suchhydrogen-rich streams contain a limited amount of at least onedemethylizable hydrocarbon impurity such acyclic hydrocarbons havingfrom 2 to about 6 carbon atoms, particularly parafiins and olefins. Forexample, hydrogen-rich off-gas streams obtained from reformer operationsordinarily contain light paraffinic hydrocarbons, whereas residue gasesobtained from light hydrocarbon cracking operations containdemethylizable olefinic hydrocarbons. Any impure hydrogen streamcontaining demethylizable hydrocarbon materials that are demethylizableat temperatures ranging from about 500 to about 750 F. can be employedaccording to the invention.

The impure hydrogen streams that I utilize as the reducing medium willcontain up to about 12 mol percent demethylizable hydrocarbons, normally4 to 8 mol percent. When the demethylizable impurities are below about 2mol percent (based on ethane realizing that propane, butane, pentane,and hexane, respectively, have about 2, 3, 4, and 5 times the heatproduced by demethylization as compared to ethane), it is not necessaryto dilute the reactivation process by recycle of the methane-hydrogenproduced in the reactivation step. When, however, the demethylizablecomponents are present in the hydrogen source above about 2 mol percent(based on ethane as stated above), recycle is required. This can beaccomplished by recycling a portion of the reactor effluent (hydrogenand methane only) and bleeding off the remaining portion to allow freshhydrogen to be brought into the system. This then allows control ofconcentration of demethylizable material in the reactor charge (orhydrogen concentration) and bed heating rates. When the demethylizableimpurities are above about 2 mol percent, an inert gas, e.g. nitrogen,methane, etc., can be utilized to dilute the reducing medium as asubstitute for recycle operation.

In actual operation, when an impure hydrogen stream containingdemethylizable hydrocarbon material(s) contacts the metal hydrogenationcatalysts to be reduced at temperatures above about 500 F., rapiddemethylation of the C and heavier hydrocarbons in the hydrogen streamoccurs. The demethylation reaction is highly exothermic. Thus, accordingto the invention, the heat of demethylation of the hydrocarbons presentin the hydrogen stream is used along with the heat in the circulatingstream to bring the catalyst bed to the desired reduction temperature.As indicated above, the quantity of demethyliza-ble material employed inthe hydrogen stream can be regulated to control the rate of heating ofthe catalyst bed.

Catalysts that can be activated or reduced with impure hydrogenaccording to the invention can be any of the Well-known metalhydrogenation catalysts, either supported or unsupported. However,nickel-kieselguhr catalysts are preferred since they are quite activefor the hydrogenation of aromatic hydrocarbons, especially benzene.Other active hydrogenation catalysts that can be reduced according tothe invention include Raney nickel, copper chromite, finely dividedplatinum, finely divided palladium, chromium oxide and the like.

The catalysts that can be activated according to the invention are wellknown and methods for their preparation are also Well known. Thenickel-kieselguhr catalysts, which are preferred for the hydrogenationof henzene, can be prepared by saturating kieselguhr with a reduciblemetal compound such as nickel hydroxide after which at least a portionof the nickel compound in the mixture is reduced to elemental nickel bycontacting same with a stream of impure hydrogen according to theinvention. As indicated above, the activation temperature ranges fromabout 500 to about 750 F. or higher for these catalysts. as hereinbeforedescribed are in a state of high activity because such treatment reducesat least a part of the nickel compound to elemental nickel, generally 35to 40 percent of the nickel being reduced, the reduced nickel content,however, sometimes varying from approximately to 50 percent. The metalhydrogenation catalysts activated according to the invention can be onother supports such as silica gel, alumina, and other knownhydrogenation catalyst supports.

As indicated above, the metal hydrogenation catalysts, and particularlynickel-kieselguhr catalysts, are effective for the hydrogenation ofaromatic hydrocarbons to saturated hydrocarbons, particularly theconversion of henzene to cyclohexane. Ordinarily, the hydrogenationreaction is carried out at a temperature in the range 200 to 600 F. andat a pressure ranging from 300 to 600 p.s.i.g. As another feature ofthis invention, the impure hydro gen stream employed for activation ofthe catalyst can also be utilized as the hydrogen stream duringhydrogenation of the aromatic hydrocarbon or other material subsequentlyhydrogenated with the activated catalyst.

A better understanding of the invention will be obtained upon referenceto the accompanying drawing which schematically illustrate theinvention.

Referring now in detail to the drawing, the system The nickel-kieselguhrcatalysts activated 4 shown essentially comprises a furnace 10, areactor 15 containing a bed of a metal catalyst to be reduced, a cooler20, a separator 25 and a compressor 30.

According to the invention, an impure hydrogen stream containingdemethylizable paraffinic hydrocarbons (C C hydrocarbons) obtained froma reforming operation is introduced into the system by way of valvedline 11. The impure hydrogen stream is passed by way of line 12 throughfurnace 10 wherein the impure hydrogen stream is heated to a temperatureabove about 500 F. The heated impure hydrogen stream is removed fromfurnace 10 by way of line 16 and introduced into the top of reactor 15containing a bed of fresh nickel-kieselguhr hydrogenation catalyst. Whenthe reformer impure stream introduced into reactor 15 contacts thenickelkieselguhr hydrogenation catalysts at temperatures above about 500F., rapid demethylization (exothermic) of the ethane and heavierhydrocarbons in the hydrogen stream occurs. This demethylation process,giving off heat, is sufiicient to raise the catalyst bed temperature tothe desired reduction temperature which is ordinarily of the order ofabout 650 to about 725 F. The impure hydrogen stream, after contactingthe catalyst bed in reactor 15, is removed from a lower portion of thereactor by way of line 18. This stream is comprised primarily ofhydrogen and methane. If desired, a portion of the gas stream removedthrough line 18 can be recovered as fuel gas by way of valved line 22.

The remainder of the reducing gas removed from reactor 15 is passed byway of valved line 19 to cooler 20 wherein the temperature of the gas isreduced to a temperature of about F., and then passed through line 21and introduced into separator 25. Condensed water is removed from alower portion of separator 25 by way of line 23, and fuel gas is takenoverhead by way of line 24. All of the fuel gas can be removed from thesystem through valved line 27 if desired. However, if desired, all or aportion of the fuel gas taken overhead from separator 25 can be passedthrough valved line 26 and combined with fuel gas in line 22 and passedto a subsequent place of utilization. A gas steam comprising hydrogenand methane is removed from separator 25 by line 28, compressed incompressor 30, and then passed through valved line 29 to line 12 whereinit is combined with impure hydrogen introduced into the system throughline 11, and thence to furnace 10 as previously described.

If one does not have a reformer residue gas rich in hydrogen, but has aresidue gas available from a process wherein light hydrocarbons arecracked, which gas contains very little ethane and heavier hydrocarbons,such a stream can also be used according to the invention. Such a streamwould also be introduced by way of valved line 11, passed throughconduit 12, heater 10 wherein it is heated to a temperature of about 500F., and thence through line 16 and introduced into reactor 15 containinga catalyst to be reduced. Since this stream contains very little ethaneand heavier hydrocarbons it gives a relatively low temperature rise dueto demethylation since only a small amount of demethylation occurs andtherefore the reduction reaction can be readily controlled. The reduc--ing gas is removed from reactor 15 through line 18 and passed forfurther use through valved line 22. When employing such a residue gas asdescribed in this embodiment it can be passed on a once-through basisthrough the reactor, no steam diluent is needed, and the gas need not berecycled as diluent as previously described in the previously describedembodiment.

' Still further according to the invention, if one does not have animpure hydrogen stream containing demethylizable hydrocarbons from aprocessing unit, but has a limited amount of pure hydrogen available andlight hydrocarbons, I provide a process wherein an impure hydrogenstream can be formed and utilized as the reducing medium. In such anoperation, pure hydrogen is introduced into the system through valvedline 13, passed through line 12, heated in furnace to a temperature ofabout 500 F, passed through line 16 and introduced into reactorcontaining a catalyst to be reduced. The hydrogen is circulated throughreactor 15, conduit 18, and back to conduit 12 and back to reactor 15until the outlet temperature of reactor 15 reaches a level above theWater dew point of the system, i.e., so that water produced in reducingthe metal oxide to the metal and water evaporated from the bed will notcondense therein, and the temperature of the bed has reached the pointwhere demethylation will take place. When the system has reached thispoint, hydrocarbon impurities, for example demethylizable materials suchas C to C acyclic hydrocarbon, are introduced into the system incontrolled amounts by Way of valved line 14. The addition of thedemethylizable materials to the circulating stream increase the rate ofheating due to the demethylation reaction (exothermic). This stream iscirculated until the desired degree of catalyst reduction isaccomplished. The heat of the demethylation of the added hydrocarbons isused along with the heat in the circulating hydrogen stream to bring thecatalyst bed to the reduction temperature which is about 700 F. Thequantity of the demethylatable hydrocarbon used can be controlled tocontrol therate of heating of the bed.

After the catalyst has been activated with the impure hydrogen stream ofthe invention as described above, the catalyst is now available forutilization for hydrogenation, e.g., aromatic hdyrocarbons. Thehydrogenation process for which these catalysts can be used is wellknown to those skilled in the art and need not be discussed furtherhere.

A more comprehensive understanding of the invention can be obtained byreferring to the following illustrative example which is not intended,however, to be unduly limitative of the invention.

Specific example An impure hydrogen stream containing demethylizablehydrocarbons obtained as olf-gas from a catalytic reformer operation isutilized Without steam to activate a fixed bed of freshnickel-kieselguhr catalyst according to the process flow shown in thedrawing. The activation temperature in reactor 15 is maintained betweena reduction temperature of about 650 F. to about 725 F. The compositionsof the various streams shown in the drawing are set forth in Table Ibelow:

0 added as diluent. The compositions of streams 11 and 18 (referring tothe drawing) are set forth in Table II below:

TABLE II.OLD WAY: SAME H2 SOURCE, NO RECYCLE, USING STEAM The catalystactivated with steam addition has a catalyst life for benzenehydrogenation of from 9 to 10 barrels of fresh feed per pound ofcatalyst.

Reasonable variations and modifications of this invention can be made,or followed, in view of the foregoing, Without departing from the spiritor scope thereof.

I claim:

A process for hydrogenating aromatic hydrocarbons which comprisescontacting said hydrocarbon under hydrogenation conditions including atemperature in the range of 200 to 600 F. with a nickel-kieselguhrcatalyst, said catalyst having been activated by heating an impurehydrogen stream containing from 2 to 12 mol percent of demethylizableacyclic hydrocarbon compounds having from 2 to 6 carbon atoms to atemperature of about 500 F., passing said heated stream over a bed ofsaid catalyst to reduce said catalyst and demethylate said hydrocarbon,thereby raising the catalyst bed temperature to a temperature in therange 650 to 725 F., removing said stream comprising hydrogen, methaneand moisture from said bed and cooling same, passing said cooled streamto a separation zone wherein condensed moisture is removed and a portionof the non-condensible materials are recovered as fuel gas, andrecycling the remainder of said stream along with said impure hydrogenstream to said catalyst bed thereby controlling the reducing temperaturein said range of 650 to 725 F. and the quantity of demethylizablecomponents passing over said bed of catalyst.

TABLE I.INVENTION: NO STEAM AND WITH REOYCLE Line 11 Recycle Line 16,Line 18, Line 27, Component Line 29, sot/Day sci/Day Set/Day S.c.f./ M01sci/Day Day Percent Hydrogen 129, 603 90. 0 1, 230, 000 1, 359, 603 1,293, 500 63, 500 Methane- 4, 900 3. 4 626, 000 630, 900 663, 500 37, 500Ethane- 3, 310 2. 3 3, 310 Propane. 3, 450 2. 4 3, 450 But-ones. 1,730 1. 2 1, 730 Pentanes 575 0. 4 575 Hexanes 432 0. 3 432 Steam (FormedSteam (Evap.)

Total 144, 000 100. 0 1, 856, 000 2, 000, 000 2, 009, 500 101,000

References Eited by the Examiner UNITED STATES PATENTS 3,098,829 7/1963White et al. 208-4255 3,130,240 4/1964 Stark 260-6839 DELBERT E. GANTZ,Primary Examiner.

ALPHQNSO D. SULLIVAN, Examiner.

